Welcome to Chemplex Industries, Inc.

1-800-4-Chemplex
(1-800-424-3675)

HOW TO SELECT A THIN-FILM SAMPLE SUPPORT WINDOW

Few thin-film materials have the necessary combination of gauge thinness, chemical resistance to sample attack, tensile strength and low mass attenuation coefficient values to effectively serve as thin-film windows. Since 1971 Chemplex® has been deeply involved in developing many thin-film products satisfying this need and extending the range and convenience of use including continuous rolls, pre-cut squares, pre-cut circles to SpectroMembrane® Carrier frames that completely eliminate annoying static cling and contamination issues.

Thin-film selection is greatly simplified by a three-step approach. The first step entails evaluating the resistance of a thin-film against chemical attack by a sample. The second step relates comparing the % Transmittance of a thin-film and gauge for the analyte-line of interest. Essentially, higher % Transmittance values denote less x-ray absorption, higher levels of detectability and smaller integration times. The third step provides choices for thin-film configurations: rolls, perforated rolls, pre-cut circles and SpectroMembrane® Carrier Frames.

Step 1

The first step in the selection process is determining the resistance of a thin-film to chemical attack by the sample, especially liquids. The following table simplifies the process. The top row indicates the chemical classification of sample substances and the various thin-film materials. Identify the chemical classification of the sample from the first column titled Chemical Classification. Scan across that row to one or more columns illustrating the highest rating of the thin-film simply expressed by Excellent, Good, Fair, Not recommended and Unknown. The thin-film related to the rating is directly read from the column headings.

 

Chemical Grouping

Mylar®

Poly-Carbonate

Etnom®

Zythene®

Poly-Propylene

Polyimide

(Kapton®)

Prolene®

Ultra-Polyester®

Acid,   dilute or weak

Good

Good

Good

Good

Excellent

N/R

Good

Good

Acids,   Conc.

Good

Good

Good

Good

Excellent

N/R

Excellent

Good

Alcohols,   aliphatic

N/R

Good

Good

Good

Excellent

Good

Excellent

N/R

Aldehydes

Unknown

Fair

Fair

Fair

Excellent

Excellent

Excellent

Unknown

Alkalies,   conc.

N/R

N/R

Good

Good

Excellent

Excellent

Excellent

N/R

Esters

N/R

N/R

Fair

Fair

Good

Good

Good

N/R

Ethers

Fair

N/R

Fair

Fair

N/R

Unknown

N/R

Fair

Aliphatic Hydrocarbon

Good

N/R

Excellent

Excellent

Good

Excellent

Good

Good

Aromatic   Hydrocarbon

N/R

N/R

Excellent

Excellent

N/R

Excellent

N/R

N/R

Hydrocarbon   Halogenated

Fair

N/R

N/R

N/R

N/R

Fair

N/R

Good

Ketones

N/R

N/R

Good

Good

Good

Good

Good

N/R

Oxidizing   agents

Fair

N/R

Fair

Fair

Fair

N/R

Fair

Fair

 N/R = Not Recommended

IMPORTANT: Some window materials may not be suitable for analyzing sulfur in diesel fuel, gasoline and other petroleum products containing aromatic hydrocarbons. ASTM D-6445-99 (Reapproved 2004) e1: “Samples of high aromatic content may dissolve polyester and polycarbonate films. In these cases, other materials besides these films may be used for X-ray windows, provided that they do not contain any elemental impurities. An optional window material is polyimide film. While polyimide film absorbs sulfur x-rays more than other films, it may be a preferred window material as it is much more resistant to chemical attack by aromatics and exhibits higher mechanical strength.”  ASTM D 4294-08a: “Any film that resists attack by the sample, is free of sulfur, and is sufficiently X-ray transparent can be used. Film types can include polyester, polypropylene, polycarbonate, and polyimide. However, samples of high aromatic content can dissolve polypropylene, polycarbonate and polyester.” Chemplex Industries, Inc., assumes no liability whatsoever in the purchase and use of any thin-film sample support window film regardless of configuration, suggested uses and  applications, claims, reports, exhibits, advertised or written or orally expressed or insinuated. Judicious testing and evaluation is strongly recommended before purchase, use and acceptance of these products. Samples are available at no charge for evaluation purposes.

 

® Etnom, Prolene, Zythene, UltraPolyester, SpectroMembrane and Chemplex are registered trademarks of Chemplex Industries, Inc.

® Mylar and Kapton are registered trademarks of E.I. DuPont de Nemours and Co., Inc.

Step 2

This step indicates the performance of a thin-film in permitting an analyte-line permeation expressed as % Transmittance values. Some thin-films are available in different gauges that reflect their influence on % Transmittance. Briefly, the highest % Transmittance value represents the most sought choice. Analyte-lines are expressed in energy, KeV for EDXRF instruments and wavelength, Ångstrom units for WDXRF analysis. In the event the spectral line of interest is unknown, the following link is helpful http://csrri.iit.edu/periodic-table.html. Simply click on the element of interest for its energy expressed in KeV units. The KeV values are easily converted to Ångstroms from the following relationship: Ångstroms = 12.39/KeV. 

Thin Film Transmittance Chart

Step 3

Chemplex offers thin-film substances in a variety of configurations to satisfy: economic, convenience, or contamination reasons. For these purposes thin-films are available in continuous rolls in dispensers with cutting edges, continuous rolls but perforated at 3” lengths to form 3” squares, pre-cut circles on special lint-free paper that serves as carriers and SpectroMembrane® Carrier Frames. With the exception of SpectroMembrane all other configurations are inherently static charged justifying the “annoying static cling” expression. SpectroMembrane consists of a thin-film perforated in a circular line pattern mounted on a paper frame. In the sample cup attachment procedure the frame automatically detaches from the frame leaving a circular thin-film affixed to the sample cup. Contamination issues are completely averted attributed to limiting personal contact through manipulation of the frame. And, there are no “annoying static cling” issues.